Small internal combustion engines are used in a wide variety of applications including for example, lawn mowers, lawn tractors, snow blowers, power machinery and the like. Frequently, such internal combustion engines employ a fuel tank for storing liquid fuel. When situated within the fuel tank, certain amounts of liquid fuel typically becomes vaporized as hydrocarbons, particularly when temperatures within the tank rises, when the tanks experience high levels of jostling, and/or when the volume within the tank unoccupied by fuel (and filled with air) becomes rather large relative to the air space. The vaporization of fuel continues even during the normal course of storage of the fuel within the fuel tank.
During engine operation, fuel from the fuel tank is supplied to the engine. Typically, fuel is supplied from the fuel tank to the engine by virtue of receiving air into the fuel tank from the atmosphere to replace the fuel. In many engines, atmospheric air can be received via a vent tank cap. Although the vent tank cap allows air into the fuel tank to supply fuel to the engine, it additionally allows fuel vapors from the fuel tank to enter the environment, thereby contributing to evaporative emissions from such engines. Thus, such emissions from the fuel tanks particularly occur when passage(s) are formed that link the interior of the fuel tank with the outside atmosphere, for example, for venting purposes as well as when refueling occurs.
Such venting of fuel vapors although not desired, is generally essential to avoid damage to the fuel tank and various other components associated with the fuel tank (e.g., the fuel tank system) and additionally to provide a supply of fuel to the engine. However, the venting of the fuel vapors can contribute to ozone and urban smog and otherwise negatively impact the environment. In fact, certain federal or state regulations, such as the California Air Resource Board regulations, prohibit venting of fuel vapors directly into the atmosphere. Thus, increasingly it is desired that these evaporative emissions from fuel tanks be entirely eliminated or at least substantially reduced.
Accordingly, to address concerns relating to fuel vapor emissions, various options have been proposed in the past. For example, at least some conventional mechanisms involve employing a sealed fuel tank cap such that any fuel vapors are vented to or from the tank through a carbon canister, which typically is a unitary enclosure that contains a material for filtering fuel vapors. The carbon canister is generally mounted separate and away from and above the fuel tank. Although the usage of carbon canisters eliminates or at least reduces the emissions of fuel vapors into the environment, they are inadequate in at least some aspects. For example, when an engine is operated or maintained in a variety of positions and/or angles, the use of carbon canisters for facilitating venting operations can add complexity to the design of the overall fuel system. In addition, certain angled positions can allow the liquid fuel in the tank to move such that it can enter the carbon canister and subsequently leak out through an atmospheric vent in the carbon canister.
Another conventional option employs a rollover valve. When a rollover valve is situated in a vent path (e.g., a path within the engine for venting the fuel vapors into the atmosphere) of an engine, the valve is oriented such that the vent path is closed off when the engine is situated at a predetermined angle. When the vent path is closed off, the amount of fuel that can leave the tank and pass through to the engine is limited. Limiting the amount of fuel to the engine undesirably limits the performance of the engine.
Furthermore, the usage of rollover valve(s) and carbon canister(s) adds complexity to the fuel system either in the fuel tank design or due to utilization of additional components such as, various brackets and multiple hoses that are required for the operation of such devices (e.g., the rollover valve and the carbon canister). These additional components can add to the overall cost of the engine and can further require various vehicle and engine design accommodations to provide for the bulky equipment and necessary positioning of the equipment. These components are also susceptible to damage and malfunction. For example, when used on a lawn mower engine, the components can be dragged against or otherwise ensnared with brush, tree branches or ground. In addition, rollover valves have moving parts that can fail or operate incorrectly, and associated components, (e.g., hoses) that can deteriorate over time.
For at least these reasons, therefore, it would be advantageous if an improved system/device and/or method could be created to prevent or reduce evaporative emissions from fuel tanks, such as the fuel tanks of internal combustion engines including, for example, small off road engines (SORE). It would also be advantageous if such an improved evaporative fuel venting system/method did not affect engine performance at various angles of operation, was capable of eliminating the need for at least a rollover valve, and was more reliable, simpler and/or cost effective as compared to conventional evaporative fuel venting systems/methods.